R-Theta stage motion systems are better suited to circular, elliptic and spiral motion patterns than conventional Cartesian 2-axis XY linear translation stages.
PI offers three classes of R-Theta stages.
- For the highest performance and precision, Air Bearing linear stages and air bearing rotary tables are used.
- Hybrid R-Theta systems use linear motor driven stages with mechanical bearings and direct-drive air bearing rotary tables.
- Direct Drive linear motor stages and direct drive rotary tables with mechanical bearings are also available.
R-Theta systems often find applications in precision laser / semiconductor applications due to higher throughput, higher precision and smaller footprint.
High Speed Motion Controllers
The stages are operated by PI’s ACS-based industrial motion controllers with ultra-fast triggers for synchronization with external equipment such as cameras, sensors or lasers. The fast controllers allow highly precise triggering with 0.01% time tolerance between signals. Trigger signals can be derived off absolute encoders or analog signals (sin/cos encoder), enabling higher precision, safer, and simplified solutions as compared to outdated digital encoder-only triggers. With the modern PI motion controllers, a trigger in an R-Theta configured system will work just as well as an XY position trigger, with the coordinate specifications simply defined in polar coordinates.
Related Glossary Terms
- linear motor
Functionally the same as a rotary motor in a machine tool, a linear motor can be thought of as a standard permanent-magnet, rotary-style motor slit axially to the center and then peeled back and laid flat. The major advantage of using a linear motor to drive the axis motion is that it eliminates the inefficiency and mechanical variance caused by the ballscrew assembly system used in most CNC machines.
Minimum and maximum amount a workpiece dimension is allowed to vary from a set standard and still be acceptable.